// tab切换
var five7 = document.querySelectorAll(".five7");
var five5 = document.querySelectorAll(".five5");
console.log(five7);
console.log(five5);

for (var i = 0; i < five7.length; i++) {
    five7[i].index = i;
    five7[i].onmouseenter = function() {
        for (var i = 0; i < five7.length; i++) {
            five7[i].className = "five7";
            five5[i].className = "five5";
        }
        this.className = "five7 li2";
        five5[this.index].className = "five5 five5_1";
    }
}